Satan is a construct of Christian spiritual tradition. Satan is another name for the devil, Lucifer, and many other names attributed to this figure, Generally Satan is seen as an antithetical figure opposing the Christian monotheistic God. In Biblical lore, Satan was called Lucifer, a name which means "light bearer," and was once one of the most loved and honored angels in Heaven until he fell from favor. His pride was his downfall and his perfection as an angel characterized his charisma as a demon.
Satan is also portrayed throughout the Bible as an agent of deception: tempting Adam and Eve in the Old Testament, and Jesus in the New Testament. Satan can assume many forms (animals or other people) and in this way can fool an manipulate people.
Whether or not Satan is "real" is a question that can best be answered by saying that spiritual and religious belief systems vary greatly across cultures. The notion that Satan might exist in corporeal form is connected to the idea that God or Jesus may once have walked among humans on earth before the resurrection and that there may be a Second Coming wherein God will once more walk among humans on earth.
I think the notion of escaping sin by accepting God as one's savior and "repenting" can be seen as an easy way out for people who do terrible things. There is an awful lot of evil done in the name of religion. From a secular humanist perspective, human behavior is a matter of free will and choice: we CHOOSE to do good and are rewarded in this life with the good will of others and recognition of our good deeds. If we choose to act with harmful intent, we are punished through judicial systems of law, or we are ostracized by our community. To assume God (or a belief in God) is the only channel by which we can understand out own intentions and actions is to ignore the very real impact of our actions on other beings.
God created angels, one was named Lucifer. Lucifer was very greedy and wanted power, he was kicked out of Heaven and ended up on earth he became a demon, then when Adam and Eve were created he decided to trick them so he tricked Eve into breaking a rule and so sin was created. Now to escape sin we must believe that God is our savior and we must repent.
Whether or not satan is real depends on your worldview. The Christian faith believes in satan/lucifer/ the devil and exploits him/it as a means of forcing good behavior. Satan is the ultimate punishment for Christians who do not fall into line with their teachings and doctrine. Satan is a very real, physical entitiy that lives in a very real, physical place (hell). However, not all religions have this idea.
Judaism, for example, does not have the same concept of a "devil". “Satan” is not a sentient being, but a metaphor for the evil inclination – the yetzer hara – that exists in every person and tempts us to do wrong. There is no hell that holds this entity; rather it resides in every person, regardless of their faith.
In the world if god is their than automatically there will be devil for example to prove light is their automatically dark will be there. Hence proved